FIELD OF THE INVENTION
The invention relates to a guide device for a turbine with a guide-blade carrier installed in a turbine housing, preferably the housing of a steam turbine, and equipped with guide blades, including positioning elements for positioning and fastening the guide blades to the guide-blade carrier and for ensuring a specific installation position of the guide blades. The invention also relates to a method for producing such a guide device with positioning elements which are provided for positioning and fastening guide blades to a guide-blade carrier and which ensure a specific installation position of the guide blades.
In order to guide the drive medium of a turbine, for example the steam in the case of a steam turbine, at the correct angle onto the moving blades, a guide device is used, having guide blades which are fixed in the so-called guide-blade carrier and are mounted, together with the guide-blade carrier, in the turbine housing. It is absolutely necessary, in that case, to ensure that the guide blades are installed in an exactly aligned position. So-called intermediate pieces have heretofore been used as positioning elements which allow such an exact positioning of the individual guide blades relative to one another. However, such intermediate pieces are extremely complicated to produce, since in the first place, two solid steel rings have to be brought to the appropriate dimensions by turning on a lathe and then have to be cut up in such a way as to produce a multiplicity of individual intermediate-piece blanks. Due to cutting losses, two steel rings are required for the intermediate pieces of a guide cascade. The intermediate-piece blanks then have to undergo careful machining of their bulging or convex side and rear side, in order to give them a shape by which two successive intermediate pieces form a free space that is suitable for receiving the guide-blade root belonging to the guide blade, and moreover also makes it possible to fix the root to the guide-blade carrier through the use of a special holding groove.
The complicated shape of the intermediate pieces not only makes them complicated to produce, but may also result in quality defects if the accuracy of fit demanded is not achieved. Losses of efficiency due to an outer contour which is not optimal are also possible and the reliability of the guide-blade fastening may suffer as a result of wash-outs in the region of gaps. However, production is made complicated not only in the case of the intermediate pieces, but also in the case of guide blades, for those too have to be provided with a holding groove, the dimensions of which must be coordinated exactly with the intermediate pieces.